Voltage
Understanding voltage, its units, and its role in electrical circuits.
What is Voltage?
Voltage, also known as electric potential difference, is the electric potential energy per unit charge between two points in an electric field. It is the 'push' or 'pressure' that drives electric current through a circuit. The SI unit of voltage is the Volt (V).
Voltage Formulas (from Ohm's Law and Power)
V = I × R (from Ohm's Law)
V = P / I (from Power Law)
V = √(P × R) (from Power Law)
Where:
• V = Voltage in Volts (V)
• I = Current in Amperes (A)
• R = Resistance in Ohms (Ω)
• P = Power in Watts (W)
V = P / I (from Power Law)
V = √(P × R) (from Power Law)
Where:
• V = Voltage in Volts (V)
• I = Current in Amperes (A)
• R = Resistance in Ohms (Ω)
• P = Power in Watts (W)
Types of Voltage
| Type | Description | Common Sources |
|---|---|---|
| Direct Current (DC) Voltage | Constant polarity, flows in one direction. | Batteries, solar cells, DC power supplies. |
| Alternating Current (AC) Voltage | Periodically reverses polarity. | Wall outlets, generators, power grids. |
Common Voltage Levels
| Application | Approximate Voltage (V) |
|---|---|
| AA/AAA Battery | 1.5 |
| Car Battery | 12 |
| USB Power | 5 |
| Household Outlet (US) | 120 (RMS AC) |
| Household Outlet (Europe) | 230 (RMS AC) |
| High-voltage transmission lines | Thousands to hundreds of thousands (RMS AC) |
Frequently Asked Questions
What is the difference between voltage and current?
Voltage is the electrical potential difference that drives current, like pressure in a water pipe. Current is the flow of electric charge, like the flow rate of water in a pipe.
What is voltage drop?
Voltage drop is the reduction in electrical potential along the length of a conductor due to its resistance. Excessive voltage drop can lead to reduced performance of electrical devices.